(1) Field of the Invention
This invention relates to the disposal of acid gas produced from hydrocarbon wells, such as oil wells. Oil field engineers have ordinary skill in this art.
(2) Description of the Related Art
A problem exists in the oil field when producing hydrocarbons from strata deep within the earth. These hydrocarbons(in gas and liquid form) often contain carbon dioxide and hydrogen sulfide. As used in this application, these gases are referred to as "acid gas". The acid gas is detrimental to the hydrocarbon usage, and therefore it is desired to remove it from the produced fluid. Processes for removing it are well known.
The hydrocarbon wells will often produce water as well. The produced water also is undesirable and is separated out. The water produced with the hydrocarbons from a strata deep below the surface of the earth is not pure water. The produced water is contaminated with different dissolved and suspended matter. In most cases, the produced water is also considered a pollutant and it is undesirable that it should be released on the surface of the earth where it would pollute surface streams or underground aquifers. One method of disposing of the produced water is to inject it into a productive or non-productive porous underground formation not containing potable water. Such an underground formation hereafter is called "disposal strata".
The separated acid gas often has insufficient value to justify further treatment or purification for any further usage. Treatment is often performed to reduce pollution. Acid gas is considered to be a pollutant and the discharge of acid gas into the atmosphere is undesirable, inasmuch as it results in "acid rain".
It is not an environmental pollution to inject the produced water with absorbed acid gases into disposal strata. In fact, the terminology of "productive or non-productive porous formation" is found in the government regulations concerning the disposal of produced water.
To inject fluids into a disposal strata, often takes high pressures. Although some injection wells extending into disposal strata might achieve satisfactory injection with no more than 400 psi, it is more common that injection pressures of 1500 psi-3000 psi are required.
Prior to this invention, at least two plants or installations which absorb acid gas into water for disposal previously exist. Both of these installations use fresh water at least partially. Each of these installations use an absorption tower. Absorption towers are basically bubble towers where the gas is bubbled through water in a series of trays. I.e., the tower would contain several trays, each tray having several bubble caps for the bubbling of the gas through the water.
Neither of these prior plants operated completely on produced water. Fresh water absorbs more acid gas than the produced water. The fresh water used by these installations is from aquifers and is potable and suitable for domestic and agricultural use such as irrigation of crops. Produced water is suitable for neither drinking nor agricultural irrigation.
Fresh water, in many oil fields, is a scarce commodity and in any event, there are more productive uses for fresh water such as agricultural irrigation.